Ready-mix concrete
Ready-mix
concrete (RMC) is a type of concrete which is manufactured in a cement factory,
or specifically known as the batching plant, according to a given set of
proportions, and then delivered to a work site, by truck mounted with mixers.
This results in a precise mixture, allowing specialty concrete mixtures to be
developed and implemented on construction sites. The fist factory which
produced ready mix concrete was built in 1930s; however, the industry didn’t
begin to expand until late 80s. Since then it has continued to grow
significantly.
Ready
mix concrete is sometimes preferred over on-site concrete mixing because of the
volume it can produce with precision of proportion of mixtures and also due to
reduced work site confusion. Using a pre-determined concrete mixture reduces
flexibility, both in the supply chain and in the actual components of the
concrete.
Ready-mix
concrete is also termed as the customized concrete products for commercial
purpose. Ready-mix concrete (RMC) refers to concrete that is specifically
manufactured for delivery to the customer’s construction site in a freshly
mixed and plastic or unhardened state. Concrete itself is a mixture of Portland
cement, water and aggregates comprising sand and gravel or crushed stone. In
traditional work sites, each of these materials is procured separately and
mixed in specified proportions at site to make concrete. Ready-mix concrete is
bought and sold by volume – usually expressed in cubic meters.
Ready-mix
concrete is manufactured under controlled operations and transported and placed
at site using sophisticated equipment and methods. In 2011, there were 72,924
workers working in 2,223 companies that produced Ready Mix Concrete in the
United States.
Process of Ready-mix concrete
Ready
mix concrete has cement, aggregates, sand, water and other chemicals, which are
weigh- batched at a centrally located plant for a premium quality. The concrete
is then delivered to the construction site in transit mixers and can be used
straight away without any further treatment. The automatic plant monitors
weigh-batching, water-cement ratio, dosage of admixture, moisture content, with
precision to produce quality concrete.
All
ingredients used for the preparation of ready mix concrete are thoroughly
tested for their quality and physical properties in a well equipped laboratory
attached to the plant for conformity to relevant international standard codes.
The moisture probe determines the water content in the sand and aggregates.
This accordingly helps in fixing the proportion of water to be added for the
preparation of the mix. Trial mixes are carried out and tested to ensure that
each and every batch of concrete coming out of the plant meets various mix
designs as per the client’s requirement with different grades of concrete.
Advantages of ready-mix concrete
Following
are the advantages of ready-mix concrete:
·
Ready Mix Concrete (RMC) allows speedy
construction through programmed delivery at site, mechanized operation with
consequent economy.
·
RMC reduces the labour cost and site
supervising cost.
·
RMC comes with consistency in quality
through accurate & computerized control of sand aggregates and water as per
mix designs.
·
Production of RMC helps in minimizing
cement wastage due to bulk handling.
·
Production of RMC is relatively pollution
free.
·
Reduced project time resulting in savings
in all aspects.
·
Proper control and economy in use of raw
material resulting in saving of natural resources.
Disadvantages of ready-mix concrete
Following
are the disadvantages of ready-mix concrete:
·
The materials are batched at a central
plant, and the mixing begins at that very plant. So the travelling time from
the plant to the site is critical over longer distances. Some sites are just
too far away, which can risk that ready mix concrete may become unusable due to
setting.
·
It will generate additional road traffic.
Generally, Ready Mix Trucks are large in size and may cover lot of area in the
road blocking other traffic. Furthermore, access roads and site access have to
be able to carry the greater weight of the ready-mix truck plus load. (Green
concrete is approx. 2.5 tonne per m³.) This problem can be overcome by
utilizing so-called ‘mini mix’ companies which use smaller 4m³ capacity mixers
able to reach more-restricted sites.
·
Concrete’s limited time span between
mixing and curing means that ready-mix should be placed within 210 minutes of
batching at the plant. Modern admixtures can modify that time span precisely,
however, the amount and type of admixture added to the mix is very important.
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